The present invention is generally directed to a microfilm retrieval system and more particularly to a microfilm retrieval system which includes automatic film search control, up-down direction control, and stop-go and reset control.
One efficient type of information storage and retrieval system that has found widespread acceptance is often referred to as microfilm storage. In such systems, copies of documents and data are recorded on film such as 16mm film with the size of the recording on the film being on the order of 1mm per inch of document size. Obviously such size reduction affords a substantial reduction in document storage volume and greatly simplifies handling of the documents. Such a reduction in size necessarily inhibits direct reading of the stored documents and the usual procedure for reading them is to project the microfilm images onto a screen with their magnification to a size corresponding approximately to the original size of the document.
Because literally thousands of documents are stored on each film reel, searching for a particular document can be time consuming. Therefore, to overcome this disadvantage automatic search techniques have been developed. Unfortunately, to avoid damage to the film such techniques have incorporated film handling apparatus which move the film at a relatively low rate of speed when searching for a document to avoid breakage of the film when it is stopped. Additionally, systems for determining in which direction the film must be displaced to arrive at the desired document have been complex. In those systems which displace the film at a high rate of speed, very complicated mechanical arrangements have been necessary for disengaging the drive means and stopping the film to avoid film breakage.
It is therefore a general object of the present invention to provide an improved automatic microfilm retrieval system which affords film searching in a minimum amount of time without breakage of the microfilm.
It is a still further object of the present invention to provide an automatic film drive direction control means for a microfilm retrieval system for determining in what direction the film must be moved to arrive at a desired document.
It is a still further object of the present invention to provide an automatic stop-go and reset control means for a microfilm retrieval system for starting and stopping the film drive and for resetting the system after each document search sequence.
The present invention provides an automatic film searching and retrieval system for use with film having a plurality of frames, each frame including document images and an adjacent frame marker. The system comprises first film drive means for driving the film at a high rate of speed in a given direction, second film drive means for driving the film at a low rate of speed in a given direction and frame marker sensing means for sensing the frame markers and for providing a counting pulse for each marker sensed. The system additionally comprises programming means for preselecting a given film frame represented by a predetermined count, film drive selecting means for actuating either the first or second film drive means, means responsive to the film mark sensing means and the programming means for causing the selecting means to actuate the second film drive means when the total number of the counting pulses differs from the predetermined count by a fixed number of counts, and means for stopping the film when the total number of the counting pulses equals the predetermined count.
The invention additionally provides a film drive direction control circuit for use in an automatic film retrieval system which uses film having a plurality of frames including document images, and has frame sensing and counting means, a programmer for preselecting a given film frame represented by a predetermined count, a comparator for comparing the counting means count with the predetermined count, film drive means capable of driving the film in either a first or second direction, drive enabling means for providing a drive enabling signal and rewind enabling means for initiating a rewind command. The film drive direction control circuit comprises a first gate coupled to the comparator, to the drive enabling means and to the rewind enabling means, and responsive to a first comparator signal when the counting means count is less than the predetermined count, the enabling means drive enabling signal, and the absence of the rewind command to provide a first intermediate drive direction control signal and a first control means coupled to the first gate for providing a first film drive direction control signal in response to the first intermediate drive direction control signal to cause the drive means to drive the film in the first direction.
The film drive direction control circuit additionally comprises a second gate coupled to the comparator and to the drive enabling means and responsive to a second comparator signal when the counting means count is greater than the predetermined count and the enabling means drive enabling signal, to provide a second intermediate drive direction control signal, a third gate coupled to the second gate and to the rewind enabling means for providing a third intermediate direction control signal in response to either the second intermediate control signal or a rewind command signal, and a second control means coupled to the third gate for providing a second film drive direction control signal in response to the third intermediate direction control signal to cause the drive means to drive the film in the second direction.
The invention still further provides a film drive speed control circuit for use in an automatic film searching and retrieval system which utilizes film having a plurality of frames, each frame including document images and having an adjacent frame marker and wherein the system includes a high speed film drive means and a low speed film drive means for driving the film at high and low speeds respectively, frame marker sensing means for sensing the frame markers and for providing a marker pulse corresponding to each marker sensed, counting means for counting the marker pulses, the number of the marker pulses counted representing an actual count, programming means for preselecting a given film frame represented by a predetermined count, and comparator means coupled to the counting means and to the programming means for comparing the counts of the counting means with the predetermined count. The film drive speed control circuit comprises adding means responsive to the comparator means for adding a fixed given number of counts to the actual count to provide an augmented actual count when the actual count is less than the predetermined count and high speed actuating means responsive to the comparator means for actuating the high speed film drive means when the augmented actual count is less than the predetermined count.
The film drive speed control circuit additionally comprises low speed actuating means responsive to the comparator means for providing a low speed drive actuating signal to actuate the low speed film drive means when the augmented actual count equals the predetermined count, subtracting means responsive to the low speed drive means signal for subtracting the fixed number of counts from the augmented actual count to restore the actual count, and stopping means responsive to the comparator means for stopping the low speed drive means when the actual count equals the predetermined count.
The invention still further provides a film drive control circuit for use in an automatic film retrieval system which uses film having a plurality of frames including document images, and has frame sensing and counting means, a programmer for preselecting a given film frame represented by a predetermined count, a comparator for comparing the counting means counts with the predetermined count, film drive means for driving the film and a command unit including a go command means for generating a go command signal, a rewind command means for generating a rewind command signal, and a rewind stop command means for generating a rewind stop command signal. The film drive control circuit comprises go-enable means coupled to the comparator and to the go command means for providing a first intermediate drive comparator when the counting means count is unequal to the predetermined count, rewind enable means coupled to the rewind command means and to the rewind stop command means for providing a second intermediate drive control signal responsive to the rewind command signal and to the absence of the rewind stop command signal, and drive control means coupled to the go-enable means and to the rewind enable means for providing the drive means with a final drive control signal responsive to either the first or second intermediate drive control signals causing the drive means to drive the film.